*{padding: 0 ; margin: 0;}
body{
    height: 100%;
    border: 1px solid chartreuse;
    float: none;
}

.big_box{
    height: 630px;
    width: 1100px;
    border: 1px solid chartreuse;
    margin: 0 auto ;
    position: relative;
    display: block;
    border-radius: 10px;

}


.box {
    height: 300px;
    width: 500px;
    border: 1px solid red;
    float: left;
    margin-left: 33px;
    margin-top: 10px;
    border-radius: 20px;

}
/*.banner_img {*/
    /*height: 300px;*/
    /*padding-left: 10px;*/
    /*padding-top: 10px;*/
    /*display: block;*/
    /*float: left;*/
    /*position: relative;*/
/*}*/

.three{
    border: 1px solid rebeccapurple;
    width: 500px;
    height: 300px;
    float: left;
    margin: 10px 300px;
    border-radius: 20px;

}